This invention relates to lightweight frame structures and, more particularly, to wheels for use therein.
There are numerous structures which, if fabricated of advanced, high strength composite materials, would experience significant weight reductions. The difficulty has been in developing a composite structure which, when assembled, will maintain the integrity of the heavier and bulkier state-of-the-art structures it is intended to replace. This is particularly true in the field of wheels, most notably spoked wheels, where loads which are applied to the spokes (tension or compression) must be distributed uniformly into the rims without severe load concentration.
Static, spoked wheels can be found, for example, in virtually all gas turbine engines in the form of frames. As is well known, air passing through a gas turbine engine is transported through an annular flow path, a portion of the inner and outer walls of which are analogous to the inner and outer rims of a wheel, respectively. Webs, called "struts" support the inner and outer flow paths in their proper relationship much in the manner of the spokes of a wheel, the struts being contoured for aerodynamic considerations. Additional duct work is supported from the aforedescribed engine frame to complete the annulus. This webbed structure is commonly known as a "fan frame" when air pressurized by a gas turbine engine fan is designed to pass therethrough. Presently, most engine frames are made of welded sheet metal or metal castings. Since weight is a critical consideration in aircraft gas turbine engine development, a composite frame structure would appear particularly attractive if the weight reduction could be achieved without penalty to structural integrity.
A composite frame structure is taught and claimed in co-pending U.S. Pat. application Ser. No. 522,108, by Adamson et al, filed Nov. 8, 1974, and assigned to the assignee of the present invention and the disclosure of which is incorporated herein by reference. Therein, the invention relates in part to an integral webbed structure resembling a spoked wheel for rigidly interconnecting the nacelle (the pod circumscribing a jet engine) and the engine itself. The nacelle is supported in its proper spacial relationship with the engine by means of the webbed structure. There is introduced, however, the problem of how to fabricate the integral webbed structure of Adamson et al., the subject of the present invention.
It is apparent that a lightweight, high strength wheel will aid not only the aircraft industry, but also will find application virtually everywhere a wheel could foreseeably be used. The situation facing industry, therefore, is to provide a lightweight, composite wheel having desirable load-bearing characteristics. The problem facing aircraft gas turbine engine manufacturers in particular is to provide a lightweight, composite structural frame which will withstand the rigors of the jet engine environment.